The invention relates to ocular prosthetic devices in general. More particularly the invention relates to an ocular prosthesis having means for adjusting the apparent pupil size or iris dilation in response to ambient light levels and a method for accomplishing same.
Eye prosthesis devices simulate the appearance of a natural eye and therefore provide a better facial appearance to someone who has lost one or both eyes. In the past a spherical or globe shaped device having an eye image on the surface was inserted in the vacant socket from which the natural eye was removed.
A much better appearance is provided, however if the artificial eye moves in tandem with a natural eye. Various methods have therefore been developed for attaching the eye movement muscle tendons to a ball shaped eye socket insert. The ball will then move in tandem with a natural eye through a well known process of sympathetic muscle action.
For example, Stafford in U.S. Pat. No. 3,364,501 describes an inflatable eye prosthesis to which six eye movement muscles are attached. Gordon in U.S. Pat. No. 5,026,392 describes a ball shaped prosthetic eye having tabs for attaching to four eye muscles. The tabs with the attached eye muscles are inserted into receiving regions on the spherical prosthetic eye. The tabs may be adjusted by removing and re-inserting into the receiving region and thereby position the eye to rest in a natural orientation with respect to the natural eye.
While an eye image may be placed on the ball itself, it is advantageous to provide a front section which is easily removable, and place the eye image on this front section. This two part construction permits the front section to be easily replaced as required. In one arrangement, the front section is substantially hemispherical so that when the prosthesis is inserted the front surface rests against the inner surface of the eyelids permitting normal opening and closing of the eyelids. The back surface rests on the ball inserted in the eye socket. A peg protruding from the ball may rest in a depression in the back surface of the front section and serve to transfer movement of the ball to the front section. Currently used materials such as light-cured urethane dimethacrylate of U.S. Pat. No. 5,326,346 or TRIAD II light cured acrylic resin supplied by Dentsply of York, Pa. of U.S. Pat. No. 5,171,265 or other acrylics are eventually attacked by body fluids in the lid area, tears etc., causing the image to deteriorate. Replacement at about five year intervals is therefore required. Removal of the front section also permits cleaning and re-insertion on a frequent basis. The difficulty of removing a front section is therefore comparable to removal of a contact lens.
Typically, a sclera, iris, and pupil matching the natural eye are painted on the ball or removable front section during manufacture by a professional person known as an ocularist. However, once painting is complete, the size of the pupil is fixed on the artificial eye. The natural eye will have a changing pupil size depending on ambient light as is well known. The ocularist therefore selects an intermediate size for the painted pupil as a best match.
Various devices and methods have been developed to provide adjustment of the pupil size in a prosthetic eye, however none are currently in wide use. Smith, in U.S. Pat. No. 3,480,971 describes a mechanical dilator which is responsive to muscle movement in the eye socket to provide control over pupil size. Danz, in U.S. Pat. No. 4,272,910 describes a fixed iris image within the body of an artificial eye. The image has a central dark portion simulating a pupil in a bright light condition. An annular ring of electro-optically sensitive material such as liquid crystal display (LCD) material is placed in front of the iris and concentrically surrounding the pupil simulating central dark portion. The outer diameter of the ring is selected to simulate the diameter of a pupil in a less than bright environment. The annular ring is normally transparent. When a photoelectric sensor detects a light level below a fixed threshold, a voltage source and switch excite the annular ring to make the pupil appear to dilate e.g. the ring becomes opaque black. Trefry and Saul in PCT application WO86/01996 describe a similar apparatus having several concentric rings which are activated in sequence as the ambient light diminishes thus simulating the pupil dilating in several steps. Boshoff, in the abstract of South Africa patent ZA 9205915 also describes a number of concentric rings of liquid crystal material activated in response to a photodiode. Majercik et al. in U.S. Pat. No. 5,108,427 also describes a series of concentric rings of a photochromic material requiring no electrical or mechanical excitation, but merely chemical reaction to incident light e.g. turning from transparent to opaque.
Schleipman et al. in U.S. Pat. No. 6,139,577 also use a series of concentric rings of LCD material to simulate a range of dilation and contraction of a pupil. In their device, however, a special pixelated iris image is created from a digital photograph of a desired natural iris by removing a number of pixels to provide clear non-image areas. The pixelated photograph is then color adjusted before printing so that it has a color and pattern approximating the natural eye when viewed in front of a liquid crystal display through the pixels. As concentric rings of the LCD are selectively activated and darkened, the portions of the pixelated iris with the activated LDC behind will appear as a pupil of various degrees of dilation.
Volker in the abstract of German patent DE 19850807A1 describes an artificial iris using overlapped color filters and a phototropic material which changes color to simulate contraction of a pupil in a bright light.
As noted above, none of these developments are in widespread use today. In accordance with the teachings of the present invention there is presented a new apparatus and method for adjusting pupil size in an ocular prosthesis. It is believed that such a device constitutes a significant advancement in the art.
Even though eye prosthesis are primarily intended for human use, it will be obvious to those of skill in the art that application will also extend to use in animals, dolls, mannequins, robots or any other objects having an eye.
It is therefore a principal object of the present invention to enhance the ocular prosthetic art by providing a device with enhanced capability.
It is another object to provide such a device which can be economically produced and widely used.
It is yet another object to provide a novel method of adjusting pupil size in an eye prosthesis.
These and other objects are attained in accordance with one embodiment of the invention wherein there is provided an adjustable iris image for an artificial eye, comprising, a color liquid crystal display positioned within the artificial eye, a memory chip coupled to the color liquid crystal display having a plurality of patterns corresponding to a plurality of iris images to be shown on the color liquid crystal display, a light sensor coupled to the memory, and means for sending in response to the light sensor, one of the plurality of patterns to the color liquid crystal display.
In accordance with another embodiment of the invention there is provided an eye prosthesis, comprising, a shell having a convex surface, a liquid crystal array display device positioned behind the convex surface and within the shell, memory means coupled to the display device having a plurality of data patterns corresponding to eye iris images with differing pupil sizes, for exhibiting on the display device, a light sensor coupled to the memory means, and a control circuit for selecting one of the plurality of data patterns in response to the light sensor and transferring the data pattern to the display device.
In yet another embodiment of the invention there is provided a method of adjusting pupil size in an eye prosthesis, comprising the steps of, providing an eye prosthesis having a substantially circular array of color liquid crystal display elements, a memory device, and a light sensing device, storing a plurality of data patterns in the memory device, the data patterns corresponding to eye iris images with differing degrees of pupil size, and sensing a level of ambient light with the light sensing device and therefrom selecting one of the plurality of data patterns in the memory device and displaying the corresponding eye iris image on the array of color liquid crystal display elements.